U.S. patent number 7,417,832 [Application Number 11/114,255] was granted by the patent office on 2008-08-26 for magnetoresistive structure having a novel specular and filter layer combination.
This patent grant is currently assigned to Western Digital (Fremont), LLC. Invention is credited to Dustin W. Erickson, Shin Funada, Lena Miloslavsky, Chang-Man Park.
United States Patent |
7,417,832 |
Erickson , et al. |
August 26, 2008 |
Magnetoresistive structure having a novel specular and filter layer
combination
Abstract
A method and system for providing a magnetoresistive structure
is disclosed. The magnetoresistive structure includes a pinned
layer, a nonmagnetic spacer layer, a free layer, a filter layer, a
specular layer, a barrier layer, and a capping layer. The
nonmagnetic spacer layer resides between the pinned layer and the
free layer. The free layer is electrically conductive and resides
between the filter layer and the nonmagnetic spacer layer. The
specular layer includes a first material and is electrically
insulating. The barrier layer resides between the specular oxide
layer and the capping layer. The barrier layer is nonmagnetic and
includes a second material different material from the first
material. The capping layer includes a third material different
from the second material.
Inventors: |
Erickson; Dustin W. (San Jose,
CA), Park; Chang-Man (Mountain View, CA), Funada;
Shin (Pleasanton, CA), Miloslavsky; Lena (Sunnyvale,
CA) |
Assignee: |
Western Digital (Fremont), LLC
(Fremont, CA)
|
Family
ID: |
39711255 |
Appl.
No.: |
11/114,255 |
Filed: |
April 26, 2005 |
Current U.S.
Class: |
360/324.1;
360/324.2 |
Current CPC
Class: |
B82Y
25/00 (20130101); G01R 33/093 (20130101); G11B
5/3906 (20130101); H01F 10/3254 (20130101); H01F
41/325 (20130101); H01F 41/32 (20130101); H01L
43/08 (20130101); H01F 10/3272 (20130101); H01F
10/3259 (20130101) |
Current International
Class: |
G11B
5/39 (20060101) |
Field of
Search: |
;360/324,324.1,324.2,324.11,324.12 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Office Action dated Jul. 11, 2007 from U.S. Appl. No. 11/114,295,
11 pages. cited by other .
Jongill Hong, et al., "Design of specularly reflective layers in
spin valves", Journal of Applied Physics, vol. 94, No. 5, Sep.
2003, pp. 3288-3291. cited by other .
Jongill Hong, et al., "Spin Valve Head With Specularly Reflective
Oxide Layers for Over 100 Gb/in2", IEEE Transactions on Magnetics,
vol. 38, No. 1, Jan. 2002, pp. 15-19. cited by other .
Tetsuya Mizuguchi, et al., "Characteristics of Spin-Valve Films
with Non-Magnetic Oxide Layers for Specular-Scattering", IEEE
Transactions on Magnetics, vol. 37, No. 4, Jul. 2001, pp.
1742-1744. cited by other .
Hitoshi Kanai, et al., "Advanced Spin-Valve GMR Head", Fujitsu Sci.
Tech. J., 37, 2, Dec. 2001, pp. 174-182. cited by other .
Office Action dated Dec. 17, 2007 from U.S. Appl. No. 11/114,295,
18 pages. cited by other.
|
Primary Examiner: Klimowicz; William J
Attorney, Agent or Firm: Strategic Patent Group
Claims
We claim:
1. A magnetoresistive structure comprising; a pinned layer; a
nonmagnetic spacer layer; a free layer, the nonmagnetic spacer
layer residing between the pinned layer and the free layer; a
filter layer, the free layer residing between the filter layer and
the nonmagnetic spacer layer, the filter layer being electrically
conductive; a specular layer, the specular layer including a first
material and being an insulator; a barrier layer, the barrier layer
being nonmagnetic, the barrier layer including a second material
different material from the first material, the barrier layer
including at least one of Pt, Ag, Au, Ru, and Re; and a capping
layer including a third material different from the second
material, the barrier layer residing between the specular layer and
the capping layer.
2. The magnetoresistive structure of claim 1 wherein the specular
layer includes titanium oxide.
3. The magnetoresistive structure of claim 1 wherein the specular
layer has a thickness of between five and thirty Angstroms.
4. The magnetoresistive structure of claim 3 wherein the thickness
of the specular layer is between six and twenty Angstroms.
5. The magnetoresistive structure of claim 1 wherein the barrier
layer has a thickness of between five and thirty Angstroms.
6. The magnetoresistive structure of claim 5 wherein the thickness
of the barrier layer is between six and fifteen Angstroms.
7. The magnetoresistive structure of claim 1 wherein the filter
layer includes at least one of Cu, Ta, Au, Ag, Pd, Ru, and Rh.
8. The magnetoresistive structure of claim 1 wherein the barrier
layer is configured to prevent intermixing between the specular
layer and the capping layer.
9. The magnetoresistive structure of claim 1 wherein the capping
layer includes Ta.
10. The magnetoresistive structure of claim 1 wherein the
nonmagnetic spacer layer is electrically conductive.
11. The magnetoresistive structure of claim 1 wherein the
nonmagnetic spacer layer is insulating.
12. The magnetoresistive structure of claim 1, wherein: the
specular layer comprises a first specular layer; and the pinned
layer comprises a second specular layer, the second specular layer
comprising an oxide.
13. A magnetoresistive structure comprising; a pinned layer; a
nonmagnetic spacer layer; a free layer, the nonmagnetic spacer
layer residing between the pinned layer and the free layer; a
filter layer, the free layer residing between the filter layer and
the nonmagnetic spacer layer, the filter layer being electrically
conductive; a specular layer, the specular layer including a first
material and being an insulator; a barrier layer, the barrier layer
being nonmagnetic, the barrier layer including a second material
different material from the first material; and a capping layer
including a third material different from the second material, the
barrier layer residing between the specular layer and the capping
layer; and wherein the barrier layer consists essentially of
Pt.
14. The magnetoresistive structure of claim 13 wherein the specular
layer comprises titanium oxide and the filter layer comprises at
least one of copper, gold, and silver.
15. The magnetoresistive structure of claim 13 wherein the specular
layer comprises aluminum oxide, and the filter layer comprises
gold.
16. The magnetoresistive structure of claim 13 wherein the specular
layer includes at least one of yittrium oxide, hafnium oxide,
magnesium oxide, aluminum oxide, nickel oxide, iron oxide,
zirconium oxide, and titanium oxide.
17. A magnetoresistive structure comprising; a pinned layer; a
nonmagnetic spacer layer; a free layer, the nonmagnetic spacer
layer residing between the pinned layer and the free layer; a
filter layer, the free layer residing between the filter layer and
the nonmagnetic spacer layer, the filter layer including at least
one of Cu, Ta, Au, Ag, Pd, Ru, and Rh; a specular layer, the
specular layer including titanium oxide; a barrier layer, the
barrier layer including Pt; and a Ta capping layer, the barrier
layer residing between the specular layer and the Ta capping
layer.
18. The magnetoresistive structure of claim 17, wherein: the
specular layer comprises a first specular layer; and the pinned
layer comprises a second specular layer, the second specular layer
comprising an oxide.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. application Ser. No.
11/114,295, entitled METHOD AND SYSTEM FOR PROVIDING A SPIN FILTER
HAVING ENHANCED RELIABILITY, filed concurrently herewith on Apr.
26, 2005, incorporated herein by reference
FIELD OF THE INVENTION
The present invention relates to magnetic recording technology, and
more particularly to a method and system for providing an improved
spin filter.
BACKGROUND OF THE INVENTION
In the effort toward achieving higher data density on recording
media, spin filters have become of interest for use in
magnetoresistive (MR) read heads. FIG. 1 is a diagram of a
conventional spin filter 10. In general, the conventional spin
filter 10 would be incorporated into a MR read head (not explicitly
shown), which would include leads electrically connected to other
electronics to drive current through the conventional spin filter
10 during reading. In such an application, current is generally
driven in the current perpendicular to the plane (CPP)
configuration. The CPP configuration is in the z-direction depicted
in FIG. 1.
The conventional spin filter 10 includes a seed layer 20, an
antiferromagnetic (AFM) layer 30, a pinned layer 40, a nonmagnetic
spacer layer 50, a free layer 60, a filter layer 70, a specular
oxide layer 80, and a capping layer 90. The seed layer 20 is used
to provide the appropriate surface for growing the AFM layer 30
with the desired crystal structure. The AFM layer 30 is used in
pinning the magnetization of the pinned layer 40. The pinned layer
40 may be a synthetic pinned layer, including ferromagnetic layers
42 and 46 separated by an electrically conductive spacer layer 44
that is typically Ru. The electrically conductive spacer layer 44
has a thickness configured to ensure that the ferromagnetic layers
42 and 46 are antiferromagnetically coupled. Thus, the
magnetization of the ferromagnetic layer 42 is pinned by the AFM
layer 30. The magnetization of the ferromagnetic layer 46 is set
because it is strongly antiferromagnetically coupled to the
magnetization of the ferromagnetic layer 42. The nonmagnetic spacer
layer 50 is typically electrically conductive, for example Cu. The
free layer 60 is ferromagnetic and typically includes materials
such as CoFe. The filter layer 80 has a high electrical
conductivity and typically includes materials such as Cu. The
specular oxide layer 80 may be a nano-oxide and typically includes
materials such as alumina. The combination of the filter layer 70
and the specular oxide layer 80 ensures adequate specularity of
scattering of electrons from the free layer 60 that are incident on
the specular oxide layer 80. Consequently, the magnetoresistance of
the conventional spin filter 10 is adequate. The capping layer 90
is typically oxidized Ta.
Although the conventional spin filter 10 functions, there are
drawbacks to the use of the conventional spin filter 10. Insertion
of the specular oxide layer 80 can increase the coercivity of the
free layer 60, which is undesirable. Furthermore, the specular
oxide layer 80 is generally a nano-oxide that can continue to
oxidize during processing. The signal may degrade during the
lifetime of the conventional spin filter 10. The conventional spin
filter 10 thus suffers thermal instabilities and may have reduced
reliability.
Analogous conventional spin filters are described in U.S. Pat. No.
6,795,279 B2; U.S. Pat. No. 6,556,390 B1; U.S. Pat. No. 5,898,612;
U.S. Pat. No. 6,407,690 B1; U.S. Pat. No. 6,764,778 B2; U.S. Pat.
No. 6,700,753 B2; U.S. Pat. No. 6,775,111 B2; U.S. Pat. No.
6,591,481; U.S. Pat. No. 6,613,380 B1; U.S. Pat. No. 6,636,398
B2.
Accordingly, what is needed is a system and method for providing a
spin filter having improved thermal stability, signal sensitivity,
and/or reliability.
SUMMARY
A method and system for providing a magnetic structure is
disclosed. The method and system comprise providing a pinned layer,
a nonmagnetic spacer layer, a free layer, a filter layer, a
specular layer, a barrier layer, and a capping layer. The
nonmagnetic spacer layer resides between the pinned layer and the
free layer. The free layer is electrically conductive and resides
between the filter layer and the nonmagnetic spacer layer. The
specular layer includes a first material and is electrically
insulating. The barrier layer resides between the specular oxide
layer and the capping layer. The barrier layer is nonmagnetic and
includes a second material different material from the first
material. The capping layer includes a third material different
from the second material.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a diagram of a conventional spin filter.
FIG. 2 is a diagram of a spin filter formed in accordance with an
exemplary embodiment of the present invention.
FIG. 3 is a diagram of a spin filter formed in accordance with
another exemplary embodiment of the present invention.
FIG. 4 is a diagram of a spin filter formed in accordance with
another exemplary embodiment of the present invention.
FIG. 5 is a diagram of a spin filter formed in accordance with
another exemplary embodiment of the present invention.
FIG. 6 is a high-level flow chart depicting a method for
fabricating a spin filter in accordance with an exemplary
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 depicts a spin filter 100 formed in accordance with an
exemplary embodiment of the present invention. For clarity, the
spin filter 100 is not depicted to scale. The spin filter 100
includes a pinning layer 120, pinned layer 130, nonmagnetic spacer
layer 140, a free layer 150, a filter layer 160, a specular layer
170, and a capping layer 180. The spin filter 100 may also include
seed layer(s) 110 used to ensure that the pinning layer 120 has the
desired crystal structure and, therefore, magnetic properties. For
example, the seed layer(s) 110 might include Ta, Ta/NiFe, NiCr,
NiFeCr or any combination thereof.
The pinning layer 120 is generally an AFM layer. The AFM materials
used in the pinning layer 120 can include, but are not limited to
PtMn, NiMn, PtCrMn, or IrMn. The pinned layer 130 is preferably a
synthetic pinned layer including ferromagnetic layers 132 and 136
separated by a spacer layer 134. The spacer layer 134 is preferably
Ru. The thickness of the spacer layer is selected such that the
ferromagnetic layers 132 and 136 are antiferromagnetically coupled.
However, another type of pinned layer 130, such as a simple pinned
layer, may be used. In the embodiment shown, the magnetization of
the ferromagnetic layer 132 is pinned by the pinning layer 120. The
magnetization of the ferromagnetic layer 136 is set based on the
coupling with the ferromagnetic layer 132 and, therefore, acts as a
reference. The nonmagnetic spacer layer 140 is preferably an
electrical conductor, such as Cu, an alloy of Cu, Ta, Pt, Au, Ag,
Pd, Ru, or other low electrical resistance material(s). In another
embodiment, the nonmagnetic spacer layer 140 may be an insulator.
In such an embodiment, the nonmagnetic spacer layer 140 is
preferably sufficiently thin to act as a tunneling barrier. The
free layer 150, as well as the ferromagnetic layers 132 and 136 may
include Co.sub.1-xFe.sub.x alloy, where x can vary from one to
ninety-nine atomic percent. However, other suitable materials, a
simple free layer, or a synthetic free layer for the free layer 150
may be used. The capping layer 190 is a capping layer, such as a Ta
layer that has been formed into a natural oxide.
The spin filter 100 also includes the filter layer 160, a specular
layer 170, a barrier layer 180, and a capping layer 190 in
accordance with the present invention. The filter layer 160 has a
low electrical resistance in comparison to the free layer 150. The
filter layer 160 preferably includes at least one of Cu, Ta, Au,
Ag, Pd, Ru, and Rh. The specular layer 170 is configured such that
current carriers from the free layer 150 tend to undergo specular
reflection by the specular oxide layer. The specular layer 170 is
preferably a nano-oxide layer and is, therefore, insulating. The
specular layer 170 has a thickness of between five and thirty
Angstroms, and more preferably a thickness of between six and
twenty Angstroms. The barrier layer 180 has a thickness of between
five and thirty Angstroms, and more preferably a thickness of
between six and twenty Angstroms.
The properties of the filter layer 160, the specular layer 170, the
barrier layer 180, and, in some embodiments, the capping layer 190
are related. In a preferred embodiment, the filter layer 160 and
the specular layer 170 are configured to preclude formation of a
solid solution and intermixing between the filter layer 160 and the
specular layer 170. The barrier layer 180 is configured to prevent
the specular layer 170 from intermixing with other layers, such as
the capping layer 190. Thus, the specular layer 170 includes a
first material. The barrier layer 180 includes a second material
different from the first material. The capping layer 190 includes a
third material different from the second material.
The materials selected for the barrier layer 180, specular layer
170, and filter layer 160 are interrelated. In one embodiment, the
barrier layer 180 includes at least one of Pt, Ag, Au, Pd, Ru, Rh,
and Re. The specular layer 170 may include at least one of yittrium
oxide, hafnium oxide, magnesium oxide, aluminum oxide, nickel
oxide, iron oxide, zirconium oxide, and titanium oxide. In a
preferred embodiment, the barrier layer 180 consists essentially of
Pt alone. Also in that preferred embodiment, the specular layer 170
includes titanium oxide and the filter layer 160 includes at least
one of copper, gold, and silver. However, other material(s) could
be used for the specular layer 170 if the barrier layer 180 is
essentially composed of Pt. For example, the specular layer 170 may
include aluminum oxide, while the filter layer 160 includes gold.
In another embodiment, if the specular layer 170 includes titanium
oxide, other materials, such as Ag, Au, Pd, Ru, Rh, and Re may be
used for the barrier layer 180. The filter layer 160 includes at
least one of Cu, Ta, Au, Ag, Pd, Ru, and Rh.
The spin filter 100 having the combination of the spin filter layer
160, the specular layer 170, the barrier layer 180, and the capping
layer 190 may have improved thermal stability and performance.
Because of the combination of the filter layer 160 and the specular
layer 170, the intermixing between the filter layer 160 and the
specular layer 170 may be reduced. Due to the presence of the
barrier layer 180, the intermixing between the specular layer 170
and the capping layer 190 may be reduced. In a preferred
embodiment, for example in which the barrier layer 180 consists
essentially of Pt, the specular layer 170 includes titanium oxide
and the filter layer 160 includes at least one of copper, gold, and
silver, the intermixing is reduced while the high signal may be
preserved. Thus, the spin filter 100 may have the desired signal
without the adversely affecting the electrical resistance or
reliability. Consequently, both the performance and the reliability
of the spin filter 100 may be improved. Moreover, it is noted that
the spin filter 100 may be used in either a CPP or CIP (current in
plane) configuration.
FIG. 3 is a diagram of a spin filter 100' formed in accordance with
another exemplary embodiment of the present invention. For clarity,
the spin filter 100' is not depicted to scale. The spin filter 100'
includes components analogous to the components of the spin filter
100. Consequently, the spin filter 100' includes a pinning layer
120', pinned layer 130', nonmagnetic spacer layer 140', a free
layer 150', a filter layer 160', a specular layer 170', a barrier
layer 180', and a capping layer 190'. The spin filter 100 may also
include seed layer(s) 110'.
The layers 110', 120', 130', 140', 150', 160', 170', 180', and 190'
preferably have the same structure and function as the layers 110,
120, 130, 140, 150, 160, 170, 180, and 190. For example, the filter
layer 160' preferably includes at least one of Cu, Ta, Au, Ag, Pd,
Ru, and Rh and has a high electrical conductivity. The specular
layer 170' is configured such that current carriers from the free
layer 150' tend to undergo specular reflection by the specular
oxide layer. The specular layer 170' is preferably a nano-oxide
layer and is, therefore, electrically insulating. The specular
layer 170' has the same thickness ranges as the specular layer 170'
of FIG. 2. In a preferred embodiment, the filter layer 160' and the
specular layer 170' are configured to preclude formation of a solid
solution and intermixing between the filter layer 160' and the
specular layer 170'. The barrier layer 180' is configured to
prevent the specular layer 170' from intermixing with the capping
layer 170'. The specular layer 170' includes a first material. The
barrier layer 180' includes a second material different from the
first material. The capping layer 190' includes a third material
different from the second material.
The materials selected for the barrier layer 180', specular layer
170', and filter layer 160' are interrelated. Preferably, the
materials used for the barrier layer 180', the specular layer 170',
and the filter layer 160' are the same as for the barrier layer
180, the specular layer 170, and the filter layer 160,
respectively, depicted in FIG. 2. Referring back to FIG. 3, the
barrier layer 180' includes at least one of Pt, Ag, Au, Pd, Ru, Rh,
and Re, but preferably consists essentially of Pt. The specular
layer 170' may include at least one of yittrium oxide, hafnium
oxide, magnesium oxide, aluminum oxide, nickel oxide, iron oxide,
zirconium oxide, and titanium oxide. The specular layer 170'
preferably includes titanium oxide and the filter layer 160
includes at least one of copper, gold, and silver. However, other
material(s) could be used for the specular layer 170' if the
barrier layer 180' is essentially composed of Pt. For example, the
specular layer 170' may include aluminum oxide, while the filter
layer 160' includes gold if the barrier layer 180' is composed
essentially of Pt. In another embodiment, if the specular layer
170' includes titanium oxide, other materials, such as Ag, Au, Pd,
Ru, Rh, and Re may be used for the barrier layer 180'. The filter
layer 160' includes at least one of Cu, Ta, Au, Ag, Pd, Ru, and
Rh.
The spin filter 100' also includes an additional specular oxide
layer 195, which resides within the ferromagnetic layer 136'. The
specular oxide layer 195 is preferably a nano-oxide layer. Thus,
the ferromagnetic layer 136' includes ferromagnetic layers 136A and
136B. The specular oxide layer 195 is configured such that current
carriers from the free layer 150' tend to undergo specular
reflection by the specular oxide layer 195.
The spin filter 100' shares many of the benefits of the spin filter
100. Thus, the spin filter 100' may have improved thermal stability
and performance. For example, because of the combination of the
filter layer 160', the specular layer 170', and the barrier layer
180', the thermal stability of the spin filter 100' may be
improved. In a preferred embodiment, using the materials described
above, the stability may be improved while the high signal may be
preserved. Consequently, both the performance and the reliability
of the spin filter 100' may be improved. Moreover, it is noted that
the spin filter 100' may be used in either a CPP or CIP (current in
plane) configuration.
FIG. 4 is a diagram of a spin filter 200 formed in accordance with
another exemplary embodiment of the present invention. For clarity,
the spin filter 200 is not depicted to scale. The spin filter 200
is analogous to the spin filter 100, but is a top spin filter.
Consequently, the spin filter 200 has layers 210, 280, 270, 260,
250, 240, 230, 220, and 290 are analogous to layers 110, 120, 130,
140, 150, 160, 170, 180, and 190, respectively. The spin filter 200
includes a pinning layer 280, pinned layer 270, nonmagnetic spacer
layer 260, a free layer 250, a filter layer 240, a specular layer
230, a barrier layer 220, and a capping layer 280. The spin filter
200 may also include seed layer(s) 210. The pinned layer 270 also
preferably includes ferromagnetic layers 272 and 276 separated by
nonmagnetic spacer layer 274.
The layers 210, 280, 270, 260, 250, 240, 230, 220, and 290
preferably have the same structure and function as the layers 110,
120, 130, 140, 150, 160, 170, 180, and 190, respectively, depicted
in FIG. 2. Referring back to FIG. 4, for example, the barrier layer
220, the specular layer 230, and the filter layer 240 preferably
have the same structure and function and include the same materials
with the same thicknesses as the barrier layer 180, the specular
layer 170, and the filter layer 160, respectively, depicted in FIG.
2.
Thus, the spin filter 200 shares many of the benefits of the spin
filter 100 depicted in FIG. 2. Referring back to FIG. 4, the spin
filter 200 having the combination of the spin filter layer 240, the
specular layer 230, and the barrier layer 220 may have improved
thermal stability and performance. Because of the combination of
the filter layer 240 and the specular layer 230, the intermixing
between the filter layer 240 and the specular layer 230 may be
reduced. Due to the barrier layer 220, the intermixing between the
specular layer 230 and underlying layers, such as the seed layer(s)
210, may be reduced. Thus, the spin filter 200 may have the desired
signal without the adversely affecting the electrical resistance or
reliability. Consequently, both the performance and the reliability
of the spin filter 200 may be improved. Moreover, it is noted that
the spin filter 200 may be used in either a CPP or CIP (current in
plane) configuration.
FIG. 5 is a diagram of a spin filter 200' formed in accordance with
another exemplary embodiment of the present invention. For clarity,
the spin filter 200' is not depicted to scale. The spin filter 200'
includes components analogous to the components of the spin filter
200. Consequently, the spin filter 200' includes a barrier layer
220', a specular layer 230', filter layer 240', a free layer 250',
a nonmagnetic spacer layer 260', a pinned layer 270', a pinning
layer 280', and a capping layer 290'. The spin filter 200' may also
include seed layer(s) 210'.
The layers 210', 220', 230', 240', 250', 260', 270', 280', and 290'
preferably have the same structure and function as the layers 210,
220, 230, 240, 250, 260, 270, 280, and 290. For example, the
specular layer 230 is preferably a nano-oxide layer including a
first material, while the barrier layer 220' includes a second
material different from the first material. In a preferred
embodiment, the barrier layer 220' consists essentially of Pt, the
specular layer 230 includes titanium oxide, and the filter layer
includes Ag, Au or Cu. However, other materials, such as those
described above, may be used.
In addition, the spin filter 200' includes an additional specular
oxide layer 295, which resides within the ferromagnetic layer 272'.
Thus, the ferromagnetic layer 272' includes ferromagnetic layers
272A and 272B. The specular oxide layer 295 is preferably a
nano-oxide layer. The specular layer 230 is configured such that
current carriers from the free layer 250' tend to undergo specular
reflection by the specular oxide layer 295.
The spin filter 200' shares many of the benefits of the spin filter
200. For example, because of the combination of the filter layer
240', the specular layer 230', and the barrier layer 220', the
thermal stability of the spin filter 200' may be improved.
Moreover, it is noted that the spin filter 200' may be used in
either a CPP or CIP (current in plane) configuration.
FIG. 6 is a high-level flow chart depicting a method 300 for
fabricating a spin filter in accordance with an exemplary
embodiment of the present invention. The method 300 is described in
the context of the spin filter 100. However, the method 300 may be
used for another spin filter consistent with the present invention.
Moreover, the method 300 is described in the context of forming a
single spin filter. One of ordinary skill in the art will readily
recognize, however, that the method 300 may be used in
simultaneously forming multiple spin filters.
The method 300 preferably commences after the pinning layer 120 has
been provided. The pinned layer 130 is provided, via step 302. Step
302 preferably includes providing the ferromagnetic layers 132 and
136, as well as the spacer layer 134. The nonmagnetic spacer layer
140 is provided, via step 304. Step 304 preferably includes
providing an electrically conductive layer, such as Cu. However, in
an alternate embodiment, an insulator forming a tunneling barrier
is provided in step 304. The free layer 150 is provided such that
the nonmagnetic spacer layer 140 resides between the free layer 150
and the pinned layer 130, via step 306. The filter layer 160 is
provided, via step 308. Step 308 fabricates the filter layer 160
such that the free layer 150 is between the filter layer 160 and
the nonmagnetic spacer layer 140. The specular layer 170 that
includes a first material is provided on the filter layer 160, via
step 310. In a preferred embodiment, the specular layer 170 is
provided in step 310 by depositing a metallic layer, then oxidizing
the metal layer. In a preferred embodiment, a plasma oxidation
process preferably from ten to three hundred seconds is used to
oxidize the specular metals. However, other oxidation processes
such as natural oxidation may have similar utility. The barrier
layer 180 is provided, via step 312. The barrier layer 180 provided
in step 312 includes a second material different from the first
material. The capping layer 190 is provided, via step 314. The
capping layer 190 includes a third material different from the
second material. In a preferred embodiment, the capping layer 190
includes Ta.
Using the method 300, the spin filter 100, 100', 200, or 200' may
be provided.
* * * * *